1. Field of the Invention
The present invention relates generally to a frequency allocation method of a wireless communication system operating in a frequency hopping mode and an apparatus therefor and, in particular, to a frequency allocation method and apparatus using a mirroring-assisted frequency hopping pattern for retransmission in a wireless communication system operating in a frequency hopping mode.
2. Description of the Related Art
Universal Mobile Telecommunications System (UMTS) is one of the third generation (3G) mobile telecommunication technologies, which has evolved from Global System for Mobile communications (GSM) and General Packet Radio Services (GPRS) and uses Wideband Code Division Multiple Access (WCDMA).
The 3rd Generation Partnership Project (3GPP), which is responsible for standardization of UMTS, is working to significantly extend the performance of UMTS in Long Term Evolution (LTE). LTE is a 3GPP standard that provides for a downlink speed of up to 300 Mbps and is expected to be commercially launched in 2010. In order to fulfill the requirements for the LTE systems, studies have been done on various aspects including minimization of a number of involved nodes in connections and placing radio protocol as close as possible to radio channels.
In current wireless communication systems, a mirroring technique is used for achieving frequency diversity gain to improve reception reliability. As a representative example, LTE uses a mirroring technique for uplink transmission in a frequency hopping mode. Particularly, in a Hybrid Automatic Repeat Request (HARQ) process, the LTE supports an inter-subframe frequency hopping with the mirroring technique for every initial transmission and retransmission to improve the reception reliability of retransmitted data.
In the current standard specification, however, the HARQ retransmission is performed in unit of 8 subframes, while a radio frame includes 10 subframes. This difference in the subframes diminishes further randomization of the frequency hopping even when using the mirroring technique, thereby resulting in a reduction of frequency diversity gain.